---
version: "1.0"
date: "2025-01-15"
author: "DWS Foldsite Team"
title: "Template Discovery System"
description: "Understanding how Foldsite finds and chooses templates"
summary: "Deep dive into Foldsite's hierarchical template discovery algorithm - learn exactly how templates are matched to content."
quick_tips:
  - "Templates are searched from most specific to most general"
  - "First match wins - more specific templates override general ones"
  - "Templates cascade down through directory hierarchies"
---

# Template Discovery System

Understanding how Foldsite discovers and chooses templates is key to building sophisticated sites. This guide explains the complete template resolution algorithm.

## The Discovery Algorithm

When Foldsite renders a page, it follows a **hierarchical search pattern** to find the best template.

### Core Principle

**Specificity wins.** More specific templates override general ones.

Think of it like CSS specificity:
```
#specific-id      (most specific)
.class-name
element           (least specific)
```

In Foldsite:
```
my-post.html           (most specific - exact file)
__file.md.html         (category + extension)
__file.document.html   (category only)
__file.html            (least specific - any file)
```

## File Type Detection

Before template discovery, Foldsite determines the content type:

### For Files

**Step 1:** Extract extension
```
blog/my-post.md  →  extension: "md"
```

**Step 2:** Map to categories
```
"md"  →  categories: ["document", "md"]
```

**Category mapping:**
```python
GENERIC_FILE_MAPPING = {
    "document": ["md", "txt", "html"],
    "image": ["png", "jpg", "jpeg", "gif", "svg"],
    "multimedia": ["mp4", "mp3", "webm"],
    "other": [...]  # Everything else
}
```

### For Folders

**Step 1:** Count file types in folder
```
photos/vacation/
  IMG_001.jpg  →  jpg: 1
  IMG_002.jpg  →  jpg: 2
  IMG_003.jpg  →  jpg: 3
  notes.txt    →  txt: 1
```

**Step 2:** Most common type wins
```
Most common: jpg (3 files)
→ categories: ["image", "jpg"]
```

## Template Search Order

### For Files: `blog/my-post.md`

**Given:**
- Path: `blog/my-post.md`
- Type: `file`
- Categories: `["document", "md"]`
- Extension: `md`

**Search order:**

1. **Exact file match** in current directory
   ```
   templates/blog/my-post.html
   ```

2. **Type + extension** in current directory
   ```
   templates/blog/__file.md.html
   ```

3. **Type + category** in current directory (most specific category first)
   ```
   templates/blog/__file.document.html
   ```

4. **Generic type** in current directory
   ```
   templates/blog/__file.html
   ```

5. **Move up one directory**, repeat steps 2-4
   ```
   templates/__file.md.html
   templates/__file.document.html
   templates/__file.html
   ```

6. **Default template** (if exists)
   ```
   templates/default.html
   ```

**First match wins!**

### For Folders: `photos/vacation/`

**Given:**
- Path: `photos/vacation/`
- Type: `folder`
- Categories: `["image"]` (most files are images)

**Search order:**

1. **Exact folder match**
   ```
   templates/photos/vacation/__folder.html
   ```

2. **Type + category** in current directory
   ```
   templates/photos/__folder.image.html
   ```

3. **Generic folder** in current directory
   ```
   templates/photos/__folder.html
   ```

4. **Move up one directory**, repeat steps 2-3
   ```
   templates/__folder.image.html
   templates/__folder.html
   ```

5. **Default template**
   ```
   templates/default.html
   ```

## Practical Examples

### Example 1: Blog Post

**Content:** `content/blog/posts/2024-my-post.md`

**Template search:**
```
1. templates/blog/posts/2024-my-post.html        ✗ Not found
2. templates/blog/posts/__file.md.html           ✗ Not found
3. templates/blog/posts/__file.document.html     ✗ Not found
4. templates/blog/posts/__file.html              ✗ Not found
5. templates/blog/__file.md.html                 ✓ FOUND!
```

**Result:** Uses `templates/blog/__file.md.html`

**Why:** Most specific template found in the hierarchy.

### Example 2: Homepage

**Content:** `content/index.md`

**Template search:**
```
1. templates/index.html                          ✓ FOUND!
```

**Result:** Uses `templates/index.html`

**Why:** Exact file match (most specific possible).

### Example 3: Photo Gallery

**Content:** `content/photos/vacation/` (folder with 50 JPG files)

**Categories:** `["image"]`

**Template search:**
```
1. templates/photos/vacation/__folder.html       ✗ Not found
2. templates/photos/__folder.image.html          ✓ FOUND!
```

**Result:** Uses `templates/photos/__folder.image.html`

**Why:** Type + category match in parent directory.

### Example 4: Deep Nesting

**Content:** `content/docs/guides/advanced/testing.md`

**Template search:**
```
1. templates/docs/guides/advanced/testing.html   ✗ Not found
2. templates/docs/guides/advanced/__file.md.html ✗ Not found
3. templates/docs/guides/__file.md.html          ✗ Not found
4. templates/docs/__file.md.html                 ✓ FOUND!
```

**Result:** Uses `templates/docs/__file.md.html`

**Why:** Climbs directory tree until finding a match.

## Template Cascade

Templates **cascade down** through directories:

```
templates/
├── __file.md.html              ← Default for ALL markdown
└── blog/
    └── __file.md.html          ← Override for blog/ only
```

**Rendering `content/about.md`:**
- Uses `templates/__file.md.html`

**Rendering `content/blog/post.md`:**
- Uses `templates/blog/__file.md.html` (more specific)

### Multi-Level Cascade

```
templates/
├── __file.md.html              ← Level 1: Site default
├── blog/
│   └── __file.md.html          ← Level 2: Blog default
└── blog/
    └── tutorials/
        └── __file.md.html      ← Level 3: Tutorial-specific
```

**Effect:**
- `content/about.md` → Level 1 template
- `content/blog/news.md` → Level 2 template
- `content/blog/tutorials/python.md` → Level 3 template

## Category Priority

Files can belong to multiple categories. **More specific categories come first.**

### Category Hierarchy

For `my-post.md`:
```
Categories: ["md", "document"]
              ↑         ↑
         specific   general
```

**Search order:**
```
1. __file.md.html        ← Most specific
2. __file.document.html  ← More general
3. __file.html           ← Most general
```

## Debug Mode

Enable debug mode to see template discovery in action:

```toml
# config.toml
[server]
debug = true
```

**Console output when visiting a page:**
```
[DEBUG] Template discovery for: blog/my-post.md
[DEBUG] Content type: file
[DEBUG] Categories: ['md', 'document']
[DEBUG] Extension: md
[DEBUG]
[DEBUG] Searching templates:
[DEBUG]   1. templates/blog/my-post.html          - NOT FOUND
[DEBUG]   2. templates/blog/__file.md.html        - FOUND!
[DEBUG]
[DEBUG] Using template: templates/blog/__file.md.html
```

### Debug Test Page

Create a test page to understand discovery:

```markdown
---
title: "Template Discovery Test"
---

# Current Template Info

**Current Path:** {{ currentPath }}

**Styles Loaded:**
{% for style in styles %}
- {{ style }}
{% endfor %}

**Metadata:**
{{ metadata }}
```

Visit this page and check the console to see which template was used.

## Edge Cases

### No Template Found

If no template matches:

**For files:**
- Foldsite serves the file directly (download)
- Useful for PDFs, images, etc.

**For folders:**
- Returns 404 error
- Need at least one `__folder.html` template

### Hidden Files

Files/folders starting with `___` are ignored:

```
content/
├── post.md              ✓ Will be rendered
└── ___draft.md          ✗ Ignored completely
```

No template search is performed for hidden content.

### Multiple Extensions

Only the last extension is considered:

```
my-file.tar.gz  →  extension: "gz"
```

Not: `tar.gz` or `tar`

## Style Discovery

Styles follow **similar logic** to templates but accumulate instead of first-match:

### Style Search for `blog/post.md`

**All matching styles are loaded (in order):**
```
1. /base.css                           ← Always loaded
2. /blog/__file.md.css                 ← If exists
3. /blog/__file.document.css           ← If exists
4. /__file.md.css                      ← If exists (from root)
5. /blog/post.md.css                   ← If exists (specific file)
```

**All found styles are included** (not just first match).

**Rendering:**
```html
<link rel="stylesheet" href="/styles/base.css">
<link rel="stylesheet" href="/styles/blog/__file.md.css">
<link rel="stylesheet" href="/styles/__file.md.css">
```

## Optimization Tips

### 1. Keep Templates at Appropriate Levels

**Good:**
```
templates/
├── __file.md.html       ← General template
└── blog/
    └── __file.md.html   ← Blog-specific customization
```

**Avoid:**
```
templates/
├── post1.html
├── post2.html
├── post3.html           ← Repetitive!
└── ...
```

### 2. Use Categories Effectively

**Good:**
```
templates/
├── __file.md.html           ← For markdown
├── __folder.image.html      ← For galleries
└── __file.document.html     ← For all documents
```

**Avoid:**
```
templates/
├── __file.html              ← Too generic
└── (nothing else)
```

### 3. Understand the Cascade

Place templates where they make sense:

**Project structure:**
```
content/
├── blog/       → Frequent posts, custom layout
├── docs/       → Technical docs, different layout
└── about.md    → One-off pages
```

**Template structure:**
```
templates/
├── __file.md.html         ← Default for one-off pages
├── blog/
│   └── __file.md.html     ← Blog-specific
└── docs/
    └── __file.md.html     ← Docs-specific
```

## Common Patterns

### Pattern: Section-Specific Layouts

Different sections need different layouts:

```
templates/
├── base.html                      ← Shared wrapper
├── __file.md.html                 ← Default content
├── blog/
│   ├── __file.md.html             ← Blog posts
│   └── __folder.md.html           ← Blog index
├── portfolio/
│   ├── __file.md.html             ← Project pages
│   └── __folder.md.html           ← Portfolio grid
└── docs/
    ├── __file.md.html             ← Documentation pages
    └── __folder.md.html           ← Docs index
```

### Pattern: Gradual Specialization

Start general, add specificity as needed:

**Phase 1: MVP**
```
templates/
├── base.html
└── __file.md.html
```

**Phase 2: Add Gallery**
```
templates/
├── base.html
├── __file.md.html
└── __folder.image.html       ← New!
```

**Phase 3: Custom Blog**
```
templates/
├── base.html
├── __file.md.html
├── __folder.image.html
└── blog/
    └── __file.md.html       ← New!
```

### Pattern: Override Single Page

Override one specific page:

```
templates/
├── __file.md.html           ← All markdown
└── index.html               ← Special homepage
```

## Troubleshooting

### Template Not Being Used

**Check:**
1. **File name** - Is it exactly right?
2. **Location** - Is it in the right directory?
3. **Extension** - `.html`, not `.htm` or `.jinja`
4. **Debug mode** - What does the console say?

**Debug:**
```bash
# Enable debug
[server]
debug = true

# Restart and check console output
```

### Wrong Template Used

**Likely cause:** More specific template exists

**Example:**
```
Want: templates/__file.md.html
Using: templates/blog/__file.md.html  ← More specific!
```

**Solution:** Update the more specific template, or remove it.

### Styles Not Loading

**Check:**
1. **Style file exists** in `styles/` directory
2. **Path matches** template expectations
3. **Browser dev tools** - Are styles being requested?

**Remember:** Unlike templates, **all matching styles load**.

## Next Steps

- **[Template System Overview](index.md)** - Basics of templates
- **[Template Helpers](template-helpers.md)** - Functions available in templates
- **[Recipes](../recipes/)** - Working examples
- **[Styles Guide](../styles/)** - CSS cascade system

Understanding template discovery gives you complete control over your site's presentation. Use it wisely!